Pressure gauges are widely utilized in a myriad of different environments for commercial and industrial applications where affording an indication of fluid pressure values is required. Depending on the instrument, values of pressure can be displayed in either digital or analog form. The primary sensing element of the gauge typically comprise a Bourdon tube having a free end that incurs a predictable displacement in response to pressure changes to which it is exposed. Typically, tube displacement is translated via a movement or amplifier to a rotatable pointer that is displaced opposite a dial of calibrated pressure values.
In semi-conductor fabricating plants, a variety of toxic and corrosive gases are utilized for the etching of silicone wafers. The gases are of supreme purity with contaminants measured in parts per billion. The specific gas flowing through a pipe line at any point in time is frequently changed requiring that extensive flushing and evacuation be deployed to completely remove any remnant of the prior gas from all equipment and accessories. To minimize retention of contaminants, industry imposes supreme material standards such as, for example, the use of super pure stainless steel and electropolished surfaces.
Because the Bourdon tube in a standard pressure gauge comprises a large dead-end cavity it tends to trap contaminants. The effect of trapping in semiconductor processing is to cause a prolonged change over time longer than would otherwise be necessary. At the same time, failure to remove all previous gas particles from a Bourdon tube being utilized can ruin and even destroy etched wafers in the course of being processed.